1. FIELD OF THE INVENTION
This invention relates to improved electrostatic precipitators for collection of dusts from industrial effluent gases.
2. DESCRIPTION OF THE PRIOR ART
The prior art electrostatic precipitators, hereafter called E.P., for dust collection from industrial effluent gases in general have the following disadvantages:
1. Dust particles of high resistivity of higher than about 10.sup.11 ohm-cm. cannot be collected, except at extremely low impractical efficiencies.
2. Relatively slow gas flow velocities and wide interelectrode spacings used necessitate E.P. of large overall dimensions, resulting in high equipment cost and large, expensive installation space.
3. Requirement of high tension voltage of 50KV or more cause electrical insulation breakdowns and necessitate the use of expensive high-tension rectifier equipment.
4. The use of such high-tension voltages and the use of non-uniform electrical fields in dust precipitation results in frequent flashovers, which necessitate using high-tension rectifier equipment of large current capacities with inherent high costs.
5. The use of negatively charged wire discharge (ionizing) electrodes, which also act as collecting electrodes for positively charged dust particles, necessitate frequent rapping of these wire discharge electrodes to remove the dust collected on the wires and thereby prevent impediment of ionization. This frequent rapping results in reentrainment of the collected dust back into the gas flow, thereby lowering the overall collecting efficiency of E.P.
6. The wire discharge electrodes become damaged from the mechanical shock and vibration of frequent rapping, and this necessitates shutdown of E.P. and expensive repair and replacement work, in addition to the inconvenience and the high cost of disruption of the manufacturing process during E.P. shutdown.
7. Generation of large quantities of harmful ozone and oxides of nitrogen because of use of negative discharge electrodes at high voltages.